1. Field of the Invention
This invention relates to an on-line, fiber optics monitor for the detection of resin fluorescence of ion exchange resin particles entrained in water. The monitor is especially useful for sensing resin leakage from condensate polishers and make-up demineralizers in steam power plants.
2. Background
Electric utilities require water of extremely high purity for the production of steam. This purity is usually achieved by the use of ion exchange systems commonly referred to as demineralizers, polishers, or deionizers.
Harmful cationic and anionic materials are removed from solution by passing the raw water through vessels containing ion exchange resins. In deep bed systems, the resin takes the form of small spherical beads (.about.1 mm. dia.). The beads are usually contained in beds in large tanks which are screened at the top and bottom. Alternatively, the resin may take the form of a powder that is coated onto tubular filters.
A common problem with such demineralizer systems is resin leakage. This occurs when resin particles are broken into small fragments by mechanical, physical or chemical action, and the fragments then pass through screens and filters designed to retain the resin. Leakage may also result from defective filters and screens or improper operation. The fines can be carried into high temperature regions of a plant where they decompose to form corrosive compounds. Both cation and anion exchange resins decompose at temperatures above 200.degree. C. to yield ionic products which can be very corrosive in both gaseous and liquid phases.
Despite the importance of detecting resin intrusions, little is available in the way of instrumentation for this purpose. The only approach which appears to have been used to date is filter collection. This approach is described in Procedure for the Measurement of Resin Fragment Leakage: Preliminary Results from the Davis Besse Nuclear Station, by S. J. Elmiger et al., Proceedings of the 41st International Water Conference, Pittsburgh, Pa, 1980, pages 250-254. This technique utilizes a collecton procedure that involves insertion of a sampling tube into the demineralizer effluent with filtering of the flow from this tube with a microporous filter having, for example, a 0.45 micron pore size. The filter is then dissolved and the volume of resin is measured in a centrifuge tube. Alternatively, the fines are counted while on the filter by microscopic examination. This type of method gives batch-wise information. The sampling can be non-representative, the technique is laborious, and non-resin particulate matter can interfere.